let num = 25;
switch(true){
    case num < 0 :
        console.log('num:'+num +' less than ' + 0);
        break;
    case num >= 0 && num < 20:
        console.log('num:'+ num + ' between 0 and 20');
        break;
    case num >=20:
        console.log('num:'+num+ ' more than 20');
        break;
    default:
        console.log('num is NaN');
}